A PBX is an automatic telephone switching system that enables users within an organization, often termed in the art a customer premise, to place calls to one another without having to access a public switched telephone network (PSTN). Users of a PBX can also place calls to outside numbers via the PBX. PBXs are typically located on the premises of a customer and provide a great deal of control and flexibility in the customer's communications. PBXs are well known in the art, and are described, for example, in “PBX Systems for IP Telephony”, by Al Sulkin, (MacGraw-Hill, NY) © 2002.
There are presently two general classes of switching system configurations available to serve the communication needs of business customers. The first is the PBX located on the customers' premises, and the second is the central office based system, e.g., CENTREX system, where lines are extended from the central office to individual customer stations but advanced features are provided by means of call processing software executed in the central office system. PBXs are considered advantageous by customers who desire a great deal of control and flexibility in their communications. Central office systems are typically preferred by customers who wish to avoid the responsibility and cost associated with operating and maintaining an on-premises switch.
Lately both the PBX and CENTREX approaches have been adapted for use in IP (Internet Protocol) based networks as well as of Time Division Multiplexing (TDM) networks. Such systems are called in general IP Telephony systems or IP-PBXs, and are described for example in U.S. Pat. No. 5,875,234, which describes a computer integrated telephony (CIT) system that integrates a PBX with a Local Area Network (LAN), and also in U.S. Pat. No. 6,424,700, which describes network-based telephone systems, and in particular systems and methods of integrating a private branch exchange (PBX) into a shared resource network.
Centralized design is used in most state of the art Telephony and IP-Telephony systems and networks. In centralized design a server (e.g. switch, access node, cabinet and so on) is executing most of system features and services. Such a centralized approach, however, is not taking full advantage of newly-available features of IP networks with vendors repeating their TDM design and applying it to IP Telephony (IPT) systems. This situation is creating technical problems and delaying market adaptation of IP Telephony in general.
According to BCR eWeekly, Issue 58—“Thinking About Next-Gen IPT”, part of the reason that it's tough to find either compelling economics or applications for IP Telephony is because vendors of such systems have tried to port the circuit-switched model into the IP world. So, not surprisingly, what IP Telephony typically delivers looks and behaves very much like what TDM delivered. Vendors also have ported the TDM cost model into IP telephony. For example, phones often account for somewhere around 30 percent of the cost of a new system. Cisco and other IP-telephony pioneers didn't try to change the cost model when they opened up this new territory, and not surprisingly, the traditional vendors haven't been eager to change it either.
The TDM design and systems approach was created out of limitations and characteristics of then-current technologies, systems and networks. For example, it was not possible to surrender system control to end-user devices and at the same time to provide efficient interconnectivity for all system features. Limitations in processing power as well as in software sophistication and lack of universal protocol for interconnect dictated the design of all Telephony Systems for the last 20 years. But the introduction of IP Telephony as well as general advancement in processor technology have made it possible for the present inventors to move on and develop a radically new and innovative design, which operates without a central system or server for controlling the call process or any additional telephony feature.
The present inventors have determined that a serverless design for IP Telephony would be very desirable, and would be ideal for substantially all basic aspects of telephony, such as call establishment delay, and for creation and adaptation of new services. Such an innovation also makes it much cheaper to communicate, and eliminates switches or servers dedicated to call control, and the cost of such equipment, making the network purely a transport for IP services, thus much easier to manage, maintain and support. Further, a purely serverless IP telephony system provides enhanced scalability, flexibility, redundancy, reliability, efficiency, cost-effectiveness and more.
Following are problems involved that have been addressed in creating such a system:
Serverless Addressing Resolution
Typically a central addressing server is used in IP Telephony systems in order to identify the called party's IP address. Each IP Telephony standard has its own name for such a server: Gatekeeper in H.323, Proxy in SIP, Call Agent in MGCP or Soft Switch in Packet Cable. Each vendor may call this server or other server that performs such functionality by a different name, but the functionality is still common. Since there is no central addressing server in the innovative system described in various embodiments in this disclosure, there is a problem for a calling party to identify a network address of the called party. The problems are greater when no permanent IP address exists on the network and such protocols as DHCP are in use.
Configuration
There is a problem with configuration of end-user devices in a serverless system since no permanent configuration server exists. These particular problems involve configuration update for any device that is out of order or unreachable at a particular time of administration update, or efficient traffic management when the system involves big numbers of such end-user devices.
Additional Services
There are large numbers of services expected from any telephony system, particularly from an IP-PBX system. For example, such features as REDIRECT, call transfer, call park, forwarding, follow me, hoteling, all of which are common terms in the art, and so on that will be described in detail elsewhere in this specification. Such services and features are significantly different in implementation within a serverless system as conceived by the present inventors, since no central call control and management server is presented for resolving possible conflicts, unavailability of specific end-user devices, or unavailability of part of the network.
Even more complicated for implementation is the group of advanced PBX features, such as Discrete Call Observing, Invite, Executive Busy Override and so on, which may involve a distributed data base for proper functioning. Roaming and related features (hoteling, follow me) also are significantly difficult for implementation in a serverless system, since there is no centralized profile data base which is not related to actual end-user device location and functioning.
Data storage-related features such as Call Record, Voice Mail and so on require storage servers (such as LDAP for example) in conventional telephony systems. In the present invention such features are handled by a distributed storage system, which is by itself innovative and a technological challenge of high degree.
Management
When no server is involved there is a particular problem of monitoring calls and monitoring quality and resources on the network without overloading the network with system messages.
Fault Tolerance
While redundancy and fault tolerance are addressed in server architecture by using well known methods, in a serverless system there is a problem of supporting the seamless work of all the end-user devices so they are not affected by sudden “death” of others.
Security
In state of the art conventional telephony systems security is handled by a special server which can be physically protected, and no connection involves another device or server which may be de-facto not protected. In a serverless system the case is quite the opposite. There is no central server and the connections possibly involve third party's end-user devices which make such a system potentially vulnerable for such security attacks as “man-in-the-middle”, and creates a problem with caller authentication, with non-repudiation of call, and so on.
So it is readily seen that there are a significant number of problems that need to be addressed in order to create a serverless IP system. In general, various conventional systems address at most a subset of the problems discussed above. There is clearly a need in the art for a system and corresponding method for solving one or more of the aforesaid problems in a comprehensive manner with a serverless system.